Table of Contents
IGP Fast ConvergenceISIS Case Study
Agenda
IGP Convergence and SLA’s
SLA
Loss of Connectivity
Historical ISIS Convergence
Factors that influence ISIS Convergence
What this presentation will explain
LinkState protocol overview
LinkState
LinkState Packet
Flooding, LSPDB
From the LSPDB to the RIB
LSDB, RIB and FIB
LSDB, RIB and FIB
LSDB, RIB and FIB
Dijkstra’s SPF computation in depth
Shortest Path First algorithm
Complexity of the algorithm
Theory is not real life !
Shortest Path First algorithm
Shortest Path First algorithm
Shortest Path First algorithm
Shortest Path First algorithm
Finding the nexthop
An example network
The linkstate database
Adjacency database (RouterA)
Shortest Path First example
Shortest Path First example
PATHS and TENT
Shortest Path First example
PATHS and TENT
Shortest Path First example
PATHS and TENT
Shortest Path First example
PATHS and TENT
Shortest Path First example
PATHS and TENT
Shortest Path First example
PATHS and TENT
Shortest Path First example
PATHS and TENT
Shortest Path First example
The Final SPT rooted at A
PPT Slide
The RIB construction
Speeding up route installation
SPF optimisations
SPF Optimizations
PRC
IncrementalSPF
IncrementalSPF
IncrementalSPF
IncrementalSPF
IncrementalSPF
SPF, PRC, ISPF: summary
Optimising ISIS/RIB and RIB/ISIS interfaces
Parallel pointtopoint adjacencies
Parallel pointtopoint adjacencies
SPF, PRC and LSPgenExponential BackOff Timers
Backoff timer algorithm
Backoff timer algorithm
Backoff timer algorithm
Example: spfinterval 10 100 1000
Default Values
TWCC: TwoWay Connectivity Check
SPF/PRC timers for Fast Convergence
LSPgen timer for Fast Convergence
LSPGen and Link Flap
LSPGen needs Intf Dampening
LSP Pacing and Flooding
LSP Pacing and Flooding
P2P mode for backtoback GE
Link Protocol Properties
Link Protocol Properties
POS – Detection of a Down Link
POS – Bringing a down link back up
POS – Best for Convergence
Other types of Links
Fast Hello’s
Operating this Design
Monitoring link/adjacency status
Before reloading a router
ISIS Monitor
ISIS Fast Convergence Design
Design Tips
Test Results
Test Scenari
PPT Slide
PPT Slide
PPT Slide
PPT Slide
SPF Duration
Down
UP
CarrierDelay
Conclusion
What this presentation has explained
Conclusion
PPT Slide
